Semiconductor sensors, e.g. pressure sensors for use in water or air under moderate temperatures and/or pressures are well known in the art.
A first type of such a pressure sensor is known for example from GB1547592A published in 1979. Typically such sensors comprise a substrate with a thinned portion (called “membrane” or “diaphragm”) upon which membrane a pressure sensitive circuit is arranged, for example a Wheatstone-bridge comprising four piezo-resistive elements. Such a substrate typically further comprises four bondpads in electrical contact with nodes of the pressure sensitive circuit, for example two supply nodes for biasing the circuit with a voltage or current, and two output nodes for sensing a voltage indicative of the mechanical pressure exerted on the membrane by the fluid. Pressure sensors come in two variants: absolute pressure sensors and relative pressure sensors. Both are well known in the art, and hence need not be described in more detail here.
Although the basic principles of semiconductor pressure sensors have remained largely the same since 1979, there is continuous ongoing development in several directions, for example to add additional functionality on the same die, such as mechanisms for compensating offset and/or digital read-out circuitry, or to make the pressure sensors suitable for harsh media.
A second type of such a sensor is an infrared sensor as can be used for example for extracting information about the chemical composition of a fluid or gas, based on a measured infrared spectrum.
It is a challenge to make the sensor assembly suitable for a harsh environment. Existing solutions can be found for example in U.S. Pat. No. 7,992,441(B2) and US2009218643(A1).
In US2007052047(A1) a solution is proposed based on Tantalum or Tantalum alloy.
U.S. Pat. No. 8,299,549 describes a layer structure with at least one noble metal layer in contact with an ohmic contact via an interconnection line.
There is always room for improvements or alternatives.